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Understanding Concave and Convex Surfaces

Mar 5, 2025

Lecture Notes: Simplifying Concave vs. Convex Rules

Introduction

  • Speaker: Scott Solomon from Board Preppers
  • Topic: Simplifying concave and convex rules for board exams
  • Objective: Prevent confusion in distinguishing concave vs. convex surfaces during exams

Key Concepts

  1. Definitions:

    • Concave Surface: Curved inward
    • Convex Surface: Curved outward
  2. Examples:

    • Glenoid Fossa: Concave
    • Head of Humerus: Convex

Upper vs. Lower Extremity

  • Both extremities follow the same concave-convex principles.
  • Focus on the upper extremity for explanation:
    • Shoulder Joint:
      • Glenoid Fossa (Concave)
      • Head of Humerus (Convex)
    • Elbow Joint:
      • Distal Humerus (Convex)
      • Proximal Forearm (Concave)
    • Wrist Joint:
      • Styloid Process of Radius/Ulna (Concave)
      • Carpal Bones (Convex)

Pattern Explanation

  • Use letters to denote surfaces:
    • A (Concave) and **X (Convex)"
    • Pattern: A X X A A X (for both upper and lower extremities)**

Open Chain vs. Closed Chain Activities

  • Open Chain:

    • Proximal end is fixed, distal end moves.
    • Moving bone dictates the rule (e.g., distal bone).
  • Closed Chain:

    • Distal end is fixed, proximal end moves.
    • Moving bone rules (e.g., proximal bone).

Application of Rules

  • Shoulder/Hip:
    • Open Chain: Convex
    • Closed Chain: Concave
  • Elbow/Knee:
    • Open Chain: Concave
    • Closed Chain: Convex
  • Wrist/Ankle:
    • Open Chain: Convex
    • Closed Chain: Concave

Study Tip

  • Memorize the pattern A X X A A X
  • Draw on whiteboards for quick reference.
  • Practice applying rules to ensure clarity during exams.

Conclusion

  • Speaker's Message: Thanks for tuning in. More instructional content coming soon.